1. Field of Invention
The present invention relates to the field of nuclear radiation detection technology, and more particularly to a method and a device for measuring radon by an electrostatic collection method without the influence of environmental temperature and environmental humidity.
2. Description of Related Arts
Radon (222Rn) in the environment is the main source of the natural radiation that is suffered by human There are various methods and various devices for measuring radon based on different principles of measurement. The radon monitor based on an electrostatic collection method is applied widely, due to high degree of automation and the ability of distinguishing energy spectrum to exclude the interference of 220Rn. The radon monitor based on the electrostatic collection method has a semiconductor detector provided on an upper portion of the measuring chamber; a high voltage is added between the wall of the measuring chamber and the semiconductor detector to form an measuring chamber to form positively charged 218 Po; the positively charged 218Po is collected to the surface of the semiconductor detector under the function of the electrostatic field. In the process of collecting, the positively charged 218Po collides with molecule and ion in the air; if the positively charged 218Po collides with negatively charged ion OH—, the positively charged 218Po and the negatively charged OH— may recombine to be electroneutral particle, which cannot be collected to the surface of the semiconductor detector by the electrostatic field; in such a manner that the detection efficiency is decreased. For increasing the detection efficiency, RAD7 radon monitor uses a drying tube to dry the air for reducing the air relative humidity lower than 10%; when the air relative humidity is lower than 10%, the detection efficiency is not affected; another scheme is to use the curve of temperature and humidity to revise the detection efficiency. These two methods for calibrating the detection efficiency of the radon monitor based on the electrostatic collection method both have certain limitations.